The invention concerns a process for the production of packaging tubes as set forth in the classifying portion of claim 1.
The manufacture of packaging tubes comprising a tube body portion formed by a single-layer or multi-layer plastic laminate, the term multi-layer plastic laminate also includes a plastic laminate containing a metallic (aluminium) barrier layer, and a tube head which is formed from a plastic material, is essentially dominated by two technologies which differ in that one of them involves joining a prefabricated tube head to a tube body portion (hereinafter also referred to as the `finished-head technology` for the sake of brevity) while in the other technology the tube head, as it is being formed, that is to say shaped, is joined to the tube body portion (hereinafter also referred to as the `moulding-on technology` for the sake of brevity). The invention lies in the field of the former, that is to say in the field of the finished-head technology.
In the tube industry, the finished-head technology has experienced a not insignificant spread. That is because the outputs of tubes (body portions with head) per unit of time are higher in comparison with the moulding-on technology. That involves simple machine operations for bringing heads and tube body portions together, relatively low levels of capital investment costs for the head/body portion joining apparatuses and the possibility of fitting the head with closures etc in the course of the process, that is to say immediately after the head/body portion connection has been made. The disadvantages of the finished-head technology lie in the very close production tolerances of the tube body portion and the head. Added to that are material compatibilities, which have to be accurately matched, between the material of the inner layer of the tube body portion and the material of the tube head, the inner layer representing the critical component of a good connection between the body portion and the head. For example the connection of a body portion comprising polyethylene or having an inner layer of polyethylene, to a tube head of the same material, is difficult to such an extent that, to overcome the difficulties involved, the shoulder of the tube head (connection from the tube body portion to the discharge nozzle of the tube) is to be provided with a barrier or a blocking layer. That critical material compatibility is an impediment to making full use of the advantages of the finished-head technology, insofar as the body portions and the heads of different materials can admittedly be prefabricated and stored, but they cannot be combined just as may be desired, for the purposes of satisfying different requirements in terms of material to be packaged.